Thin film forming apparatus and computer-readable medium

ABSTRACT

A control unit heats a reaction pipe to a load temperature by controlling a temperature-raising heater  16 , and then makes semiconductor wafers received in the reaction pipe. Next, the control unit heats the reaction pipe in which the semiconductor wafers are received to a film formation temperature by controlling the temperature-raising heater, and then forms thin films on the semiconductor wafers by supplying a film forming gas into the reaction pipe from a process gas introducing pipe. Also, the control unit sets the load temperature to a temperature higher than the film formation temperature.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 13/337,743, filed on Dec. 27, 2011, which claims a priority to andthe benefit of Japanese Patent Application No. 2010-293816, filed onDec. 28, 2010, the disclosures of which are incorporated herein in itsentirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thin film forming method, a thin filmforming apparatus, and a program.

2. Description of the Related Art

Recently, when a thin film is formed on an object, for example, asemiconductor wafer, the semiconductor wafer is required to be processedat a low temperature, and a method of forming a thin film by using, forexample, atomic layer deposition (ALD), is examined.

Various methods are suggested as such a method of forming a thin film byusing ALD, and a method of forming a thin film at a low temperature ofabout 300° C. to 600° C. by using an organic silicon (Si) source isdisclosed in, for example, Patent Document 1.

However, in a method of forming a silicon oxide film by using, forexample, ALD, in order to make a film formation temperature a lowtemperature, a material, which becomes more adsorptive as a temperaturebecomes lower, may be used as an organic Si source. However, when suchan organic Si source is used, a film formation rate at a low-temperatureportion around an opening (a furnace opening) of a processing chamber inwhich semiconductor wafers are received is increased, thereby degradingfilm thickness uniformity in an inter-surface direction of a thin film.

3. Prior Art Reference

[Patent Document 1] Japanese Laid-Open Patent Publication No.2004-281853

SUMMARY OF THE INVENTION

Considering the above and other problems, an objective of the presentinvention is to provide a thin film forming method, a thin film formingapparatus, and a program which may form a thin film having excellentfilm thickness uniformity in an inter-surface direction at a lowtemperature.

According to an aspect of the present invention, there is provided athin film forming method including: loading an object in a reactionchamber which is heated to a load temperature; and heating the reactionchamber, in which the object is loaded, to a film formation temperature,and then forming a thin film on the object by supplying a film forminggas into the reaction chamber, wherein, in the loading of the object inthe reaction chamber, the load temperature is set to a temperaturehigher than the film formation temperature.

According to another aspect of the present invention, there is provideda thin film forming apparatus including: a reaction chamber in which anobject is received; a heating unit which heats the reaction chamber to apredetermined temperature; a film forming gas supply unit which suppliesa film forming gas into the reaction chamber; and a control unit whichcontrols each portion of the film forming apparatus, wherein the controlunit heats the reaction chamber to a load temperature by controlling theheating unit, and then makes the object received in the reactionchamber, heats the reaction chamber to a film formation temperature bycontrolling the heating unit, and then forms a thin film on the objectby supplying a film forming gas into the reaction chamber by controllingthe film forming gas supply unit, and sets the load temperature to atemperature higher than the film formation temperature.

According to another aspect of the present invention, there is provideda program for enabling a computer to serve as a heating unit which heatsa reaction chamber, in which an object is received, to a predeterminedtemperature; a film forming gas supply unit which supplies a filmforming gas into the reaction chamber; and a film forming unit whichheats the reaction chamber to a load temperature by controlling theheating unit and then makes the object received in the reaction chamber,heats the reaction chamber to a film formation temperature bycontrolling the heating unit and then forms a thin film on the object bysupplying a film forming gas into the reaction chamber by controllingthe film forming gas supply unit, and sets the load temperature to atemperature higher than the film formation temperature.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention.

The objects and advantages of the invention may be realized and obtainedby means of the instrumentalities and combinations particularly pointedout hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a view showing a heat treatment apparatus according to anembodiment of the present invention;

FIG. 2 is a diagram showing a configuration of a control unit of FIG. 1;

FIG. 3 is a diagram for explaining a method of forming a silicon oxidefilm;

FIG. 4 is graphs showing a relationship among a film thickness,in-surface uniformity, inter-surface uniformity, and a boat position ofa silicon oxide film; and

FIG. 5 is a view showing a heat treatment apparatus according to anotherembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention achieved on the basis of thefindings given above will now be described with reference to theaccompanying drawings. In the following description, the constituentelements having substantially the same function and arrangement aredenoted by the same reference numerals, and a repetitive descriptionwill be made only when necessary.

Hereinafter, a thin film forming method, a thin film forming apparatus,and a program of the present invention will be explained. In the presentembodiment, a case where silicon oxide films are formed on asemiconductor wafers by using a batch-type vertical heat treatmentapparatus shown in FIG. 1 as a thin film forming apparatus of thepresent invention will be explained.

As shown in FIG. 1, a heat treatment apparatus 1 includes a reactionpipe 2 which forms a reaction chamber. The reaction pipe 2 is formed,for example, to have a substantially cylindrical shape whoselongitudinal direction is a vertical direction. The reaction pipe 2 isformed of a material having high heat resistance and high corrosionresistance, for example, quartz.

A top portion 3 having a substantially conical shape is provided at atop end of the reaction pipe 2 to decrease the radius toward the topend. An exhaust port 4 through which a gas in the reaction pipe 2 isexhausted is provided at a center of the top portion 3, and an exhaustpipe 5 is airtightly connected to the exhaust port 4. A pressureadjustment mechanism such as a valve (not shown) and a vacuum pump 127which will be explained below are provided on the exhaust pipe 5, sothat a pressure in the reaction pipe 2 is controlled to be a desiredpressure (vacuum level).

A lid 6 is disposed under the reaction pipe 2. The lid 6 is formed of amaterial having high heat resistance and high corrosion resistance, forexample, quartz. Also, the lid 6 is configured to be vertically movableby a boat elevator 128 which will be explained below. When the lid 6 israised by the boat elevator 128, a lower portion (a furnace openingportion) of the reaction pipe 2 is closed, and when the lid 6 is loweredby the boat elevator 128, the lower portion (the furnace openingportion) of the reaction pipe 2 is opened.

A thermo-container 7 is provided on the lid 6. The thermo-container 7mainly includes a heater 8 which has a planar shape and is formed of aresistance heating material for preventing a temperature in the reactionpipe 2 from being reduced due to heat dissipation from the furnaceopening portion of the reaction pipe 2, and a support 9 which has acontainer shape and supports the heater 8 at a predetermined height froma top surface of the lid 6.

Also, a rotary table 10 is provided over the thermo-container 7. Therotary table 10 serves as a holding stage on which a wafer boat 11 inwhich objects, for example, semiconductor wafers W, are received isrotatably held. In detail, a rotary strut 12 is provided under therotary table 10, and passes through a central portion of the heater 8 tobe connected to a rotation mechanism 13 for rotating the rotary table10. The rotation mechanism 13 mainly includes a motor (not shown) and arotational force introducing unit 15 which includes a rotational shaft14 airtightly passing through the lid 6 from a bottom surface to the topsurface of the lid 6. The rotational shaft 14 is connected to the rotarystrut 12 of the rotary table 10, and transmits a rotational force of themotor to the rotary table 10 through the rotary strut 12. Accordingly,when the rotational shaft 14 is rotated by the motor of the rotationmechanism 13, a rotational force of the rotational shaft 14 istransmitted to the rotary strut 12 to rotate the rotary table 10.

The wafer boat 11 is held on the rotary table 10. The wafer boat 11 isconfigured such that a plurality of the semiconductor wafers W arevertically arranged at predetermined intervals in the wafer boat 11.Accordingly, when the rotary table 10 is rotated, the wafer boat 11 isrotated, and thus the semiconductor wafers W received in the wafer boat11 are rotated. The wafer boat 11 is formed of a material having highheat resistance and high corrosion resistance, for example, quartz.

Also, a temperature-raising heater 16 formed of, for example, aresistance heating material, is provided around the reaction pipe 2 tosurround the reaction pipe 2. A temperature in the reaction pipe 2 isincreased to a predetermined temperature by the temperature-raisingheater 16, and thus the semiconductor wafers W are heated to thepredetermined temperature.

A plurality of process gas introducing pipes 17 are inserted into (thatis, connected to) a side wall around a lower end of the reaction pipe 2.In FIG. 1, only one process gas introducing pipe 17 is shown. Processgas supply sources (not shown) are connected to the process gasintroducing pipes 17, and thus desired amounts of process gases aresupplied into the reaction pipe 2 through the process gas introducingpipes 17 from the process gas supply sources. A silicon (Si) source gas(e.g., an organic Si source gas), an oxidizing gas, or the like may beused as the process gases.

The organic Si source gas is a gas for adsorbing a source (e.g., Si) tothe object, and is used in an adsorbing step which will be explainedbelow. An aminosilane gas such as diisopropylaminosilane (DIPAS),tridimethylaminosilane (TDMAS), bistertiarybutylaminosilane (BTBAS),bisdimethylaminosilane (BDMAS), bisdiethylaminosilane (BDEAS),dimethylaminosilane (DMAS), diethylaminosilane (DEAS),dipropylaminosilane (DPAS), and butylaminosilane (BAS) may be used asthe organic Si source gas.

The oxidizing gas is a gas for oxidizing the adsorbed source (Si), andis used in an oxidizing step which will be explained below. Oxygen (O₂),ozone (O₃), or vapor is used as the oxidizing gas. Also, if ozone isused as the oxidizing gas, an ozone generating apparatus for generatingozone, for example, by using oxygen as radicals, is connected to theprocess gas introducing pipe 17 for supplying ozone, and ozone generatedby the ozone generating apparatus is supplied into the reaction pipe 2through the process gas introducing pipe 17.

A purge gas supply pipe 18 is inserted into a side surface around thelower end of the reaction pipe 2. A purge gas supply source (not shown)is connected to the purge gas supply pipe 18, and a desired amount ofpurge gas, for example, nitrogen (N₂), is supplied into the reactionpipe 2 through the purge gas supply pipe 18 from the purge gas supplysource.

Also, the heat treatment apparatus 1 includes a control unit 100 forcontrolling each portion of the heat treatment apparatus 1. FIG. 2 showsa configuration of the control unit 100. As shown in FIG. 2, anoperation panel 121, temperature sensors (group) 122, pressure gauges(group) 123, a heater controller 124, a mass flow controller (MFC)control unit 125, a valve control unit 126, a vacuum pump 127, and theboat elevator 128 are connected to the control unit 100.

The operation panel 121 includes a display screen and an operationbutton, transmits an instruction of an operator to the control unit 100,and displays various pieces of information from the control unit 100 onthe display screen.

The temperature sensors (group) 122 measure a temperature of athermocouple

(T/C) provided in each zone in the reaction pipe 2, a temperature of aT/C in each zone of the temperature-raising heater 16, and a temperaturein the exhaust pipe 5, and the like, and notifies the measuredtemperatures to the control unit 100.

The pressure gauges (group) 123 measure a pressure of each portion inthe reaction pipe 2 and in the exhaust pipe, and notifies the measuredpressures to the control unit 100.

The heater controller 124 for individually controlling the heater 8 andthe temperature-raising heater 16 responds to an instruction from thecontrol unit 100, heats the heater 8 and the temperature-raising heater16 by supplying electric current to the heater 8 and thetemperature-raising heater 16, individually measures power consumptionsof the heater 8 and the temperature-raising heater 16, and notifies themeasured power consumptions to the control unit 100.

The MFC control unit 125 controls MFCs (not shown) provided in theprocess gas introducing pipes 17 and the purge gas supply pipe 18 so asfor flow rates of gases in the process gas introducing pipes 17 and thepurge gas supply pipe 18 to be the same as flow rates instructed fromthe control unit 100, measures actual flow rates of the gases, andnotifies the actual flow rates to the control unit 100.

The valve control unit 126 controls an opening degree of a valvedisposed in each pipe to be the same as a degree instructed from thecontrol unit 100. The vacuum pump 127 is connected to the exhaust pipe5, and exhausts a gas in the reaction pipe 2.

The boat elevator 128 loads the wafer boat 11 (the semiconductor wafersW) held on the rotary table 10 in the reaction pipe 2 by raising the lid6, and unloads the wafer boat 11 (the semiconductor wafers W) held onthe rotary table 10 from the reaction pipe 2 by lowering the lid 6.

The control unit 100 includes a recipe storage unit 111, a read-onlymemory (ROM) 112, a random access memory (RAM) 113, an input/output(I/O) port 114, a central processing unit (CPU) 115, and a bus 116 whichconnects all of the recipe storage unit 111, the ROM 112, the RAM 113,the I/O port 114, the CPU 115 to one another.

A set-up recipe and a plurality of process recipes are stored in therecipe storage unit 111. Only the set-up recipe is stored when the heattreatment apparatus 1 is manufactured. The set-up recipe is executedwhen a thermal model or the like is generated according to each heattreatment apparatus. Each of the process recipes is a recipe preparedfor every heat treatment (process) which a user actually performs. Forexample, each process recipe describes a change in a temperature of eachportion, a change in a pressure in the reaction pipe 2, a time when aprocess gas starts to be supplied, a time when the process gas stopsbeing supplied, an amount of the process gas which is supplied, and soon, from when the semiconductor wafers W are loaded in the reaction pipe2 to when the semiconductor wafers W having been processed are unloadedfrom the reaction pipe 2.

Examples of the ROM 112 include an electrically erasable programmableread-only memory (EEPROM), a flash memory, and a hard disc, and the ROM112 is a recording medium for storing an operation program or the likefor the CPU 115.

The RAM 113 serves as a work area or the like for the CPU 115.

The I/O port 114 is connected to the operation panel 121, thetemperature sensors 122, the pressure gauges 123, the heater controller124, the MFC control unit 125, the valve control unit 126, the vacuumpump 127, the boat elevator 128, and so on, and controls data or asignal to be input/output.

The CPU 115 which is an important element of the control unit 100executes a control program stored in the ROM 112 and controls anoperation of the heat treatment apparatus 1 according to a recipe(process recipe) stored in the recipe storage unit 111 and aninstruction from the operation panel 121. That is, the CPU 115 controlsthe temperature sensors (group) 122, the pressure gauges (group) 123,and the MFC control unit 125 to measure a temperature, a pressure, aflow rate, and so on of each portion in the reaction pipe 2, in theprocess gas introducing pipes 17, and in the exhaust pipe 5, outputs acontrol signal to the heater controller 124, the MFC control unit 125,the valve control unit 126, the vacuum pump 127, and so on based on themeasured data, and controls each portion to follow the process recipe.

The bus 116 transmits information between the portions.

Next, a method of forming a silicon oxide film by using the heattreatment apparatus 1 configured as described above will be explainedwith reference to a recipe (a time sequence) shown in FIGS. 3A through3E. In the present embodiment, as shown in FIGS. 3A through 3E, themethod includes an adsorbing step of adsorbing Si to surfaces of thesemiconductor wafers W and an oxidizing step of oxidizing the adsorbedSi. When the adsorbing step and the oxidizing step constitute one cycle,desired silicon oxide films are formed on the semiconductor wafers W byrepeatedly performing the cycle a plurality of times, for example, 100times. Also, as shown in FIGS. 3A through 3E, in the present embodiment,a case where DIPAS is used as an organic Si source gas, ozone is used asan oxidizing gas, and nitrogen is used as a diluent gas will beexemplarily explained.

First, a loading step of receiving (loading) the semiconductor wafers Was an object in the reaction pipe 2 is performed. In detail, when thelid 6 is lowered by the boat elevator 128, as shown in FIG. 3C, apredetermined amount of nitrogen is supplied into the reaction pipe 2from the purge gas supply pipe 18 and a temperature in the reaction pipe2 is set to a predetermined load temperature by the temperature-raisingheater 16.

Here, the load temperature is set to a temperature higher than a filmformation temperature which will be explained below. The loadtemperature may be set to a temperature higher by 20° C. to 80° C. thanthe film formation temperature. If the load temperature is not higher by20° C. or more than the film formation temperature in a vertical furnacewhich loads the semiconductor wafers W from downside, a temperature inthe reaction pipe 2 may be unstable at a place, e.g., a lower portion inthe reaction pipe 2, a temperature of the place being easily unstable.In detail, while the semiconductor wafers W earlier introduced into thereaction pipe 2 and received in an upper portion (e.g., a top portion)of the boat elevator 128 are easily warmed, temperatures of thesemiconductor wafers W later introduced into the reaction pipe 2 andreceived in a lower portion (a BTM portion) of the boat elevator 128 aredifficult to be increased. Meanwhile, if the load temperature is higherby 80° C. or more than the film formation temperature, temperaturehunting occurs. Although a temperature is stabilized after a sufficientamount of time passes, throughput may be reduced, thereby failing toachieve practical productivity. If the load temperature is previouslyset to a temperature higher than the film formation temperature, sincetemperatures of the semiconductor wafers W received in the BTM portionare prevented from being reduced and temperature stabilization israpidly achieved, temperatures of the semiconductor wafers W are easilyuniform. It is more preferable that the load temperature is set to atemperature higher by 30° C. to 70° C. than the film formationtemperature, and it is most preferable that the load temperature is setto a temperature higher by 40° C. to 60° C. than the film formationtemperature. In the present embodiment, as shown in FIG. 3A, the loadtemperature is set to 450° C. which is higher by 50° C. than the filmformation temperature of 400° C.

Next, the wafer boat 11 in which the semiconductor wafers W for forminga silicon oxide film are received is held on the lid 6. Thesemiconductor wafers W (the wafer boat 11) are loaded in the reactionpipe 2 by raising the lid 6 by using the boat elevator 128 (a loadingprocess).

After the loading process is completed, the reaction pipe 2 isdepressurized to a predetermined base pressure, for example, 0.266 Pa to0.4 Pa (2 to 3×10⁻³ Torr), by discharging a gas in the reaction pipe 2.In the present embodiment, the reaction pipe 2 is depressurized to 0.4Pa (3×10⁻³ Torr). Next, a pressure in the reaction pipe 2 is set to 13.3to 665 Pa (0.1 to 5 Torr), for example, to 66.5 Pa (0.5 Torr), as shownin FIG. 3B, by supplying a predetermined amount of nitrogen as shown inFIG. 3C into the reaction pipe 2 from the purge gas supply pipe 18, anda temperature in the reaction pipe 2 is set to a predetermined filmformation temperature, for example, 400° C., as shown in FIG. 3A, byusing the temperature-raising heater 16 (a stabilizing process).

When the temperature in the reaction pipe 2 is set to the film formationtemperature due to the stabilization process, the reaction pipe 2 iscooled from the load temperature higher than the film formationtemperature to the film formation temperature. As such, since thereaction pipe 2 is heated to the load temperature in the loading processin which the reaction pipe 2 is opened, and then the reaction pipe 2 iscooled to the film formation temperature in the stabilizing process inwhich the reaction pipe 2 is closed, the temperature in the reactionpipe 2 is easily maintained at the film formation temperature. Inparticular, even at the lower portion (the BTM portion) in the reactionpipe 2 where a temperature is easily reduced, the temperature in thereaction pipe 2 may be stably maintained at the same film formationtemperature as at other portions.

When the reaction pipe 2 is stabilized to the film formation temperatureand the pressure, an adsorbing step of adsorbing Si to surfaces of thesemiconductor wafers W is performed. The adsorbing step is a process ofadsorbing Si to the surfaces by supplying an organic Si source gas tothe semiconductor wafers W.

In the adsorbing step, a predetermined amount of nitrogen is supplied asshown in FIG. 3C into the reaction pipe 2 from the purge gas supply pipe18, and a predetermined amount of DIPAS is supplied as a Si source asshown in FIG. 3D into the reaction pipe 2 from the process gasintroducing pipe 17 (a flow process).

The Si source supplied into the reaction pipe 2 is heated in thereaction pipe 2 and is activated. Accordingly, when the Si source issupplied into the reaction pipe 2, the surface of each semiconductorwafer W and the activated Si react with each other, and thus Si isadsorbed to the surface of each semiconductor wafer W.

When a predetermined amount of Si is adsorbed to the surfaces of thesemiconductor wafers W, the DIPAS is no longer supplied from the processgas introducing pipe 17 and the nitrogen is no longer supplied from thepurge gas supply pipe 18. A gas in the reaction pipe 2 is discharged,and as shown in FIG. 3C, a gas in the reaction pipe 2 is discharged tothe outside of the reaction pipe 2 by supplying a predetermined amountof nitrogen into the reaction pipe 2 from the purge gas supply pipe 18(a purge, vacuum process).

Next, an oxidizing step of oxidizing the surfaces of the semiconductorwafers W is performed. The oxidizing step is a process of oxidizing theadsorbed Si by supplying an oxidizing gas to the semiconductor wafers Wincluding the adsorbed Si. In the present embodiment, the adsorbed Si isoxidized by supplying ozone to the semiconductor wafers W.

In the oxidizing step, a temperature in the reaction pipe 2 is set to apredetermined film formation temperature, for example, 400° C., as shownin FIG. 3A, by using the temperature-raising heater 16. Also, apredetermined amount of nitrogen is supplied as shown in FIG. 3C intothe reaction pipe 2 from the purge gas supply pipe 18, and a gas in thereaction pipe 2 is discharged, thereby setting a pressure in thereaction pipe 2 to a predetermined pressure, for example, 66.5 Pa (0.5Torr), as shown in FIG. 3B. A predetermined amount of oxidizing gas, forexample, ozone, as shown in FIG. 3E, is supplied into the reaction pipe2 from the process gas introducing pipe 17. Also, a predetermined amountof nitrogen is supplied as a diluent gas into the reaction pipe 2 fromthe purge gas supply pipe 18 as shown in FIG. 3C (a flow process).

Here, since the reaction pipe 2 is heated to the film formationtemperature, the ozone supplied into the reaction pipe 2 is maintainedin an activated state without losing its activated state in the reactionpipe 2. When the activated ozone is supplied into the reaction pipe 2,the Si adsorbed to the semiconductor wafers W is oxidized, and siliconoxide films are formed on semiconductor wafers W.

When desired silicon oxide films are formed on semiconductor wafers W,the ozone is no longer supplied from the process gas introducing pipe17. Also, the nitrogen is no longer supplied from the purge gas supplypipe 18. A gas in the reaction pipe 2 is discharged to the outside ofthe reaction pipe 2 by discharging a gas in the reaction pipe 2 andsupplying a predetermined amount of nitrogen into the reaction pipe 2from the purge gas supply pipe 18 as shown in FIG. 3C (a purge, vacuumprocess).

Accordingly, one cycle including the adsorbing step and the oxidizingstep ends. Next, another cycle starts from the adsorbing step again.Silicon oxide films having desired thicknesses are formed onsemiconductor wafers W by repeatedly performing the cycle apredetermined number of times, for example, 100 times.

When the silicon oxide films having the desired thicknesses are formedon the semiconductor wafers W, the semiconductor wafers W are unloaded.In detail, a pressure in the reaction pipe 2 is returned to anatmospheric pressure by supplying a predetermined amount of nitrogen asshown in FIG. 3C into the reaction pipe 2 from the purge gas supply pipe18, and a temperature in the reaction pipe 2 is maintained at apredetermined temperature, for example, a load temperature, by using thetemperature-raising heater 16. The semiconductor wafers W are unloadedby lowering the lid 6 by using the boat elevator 128.

Next, in order to demonstrate the effect of the present embodiment, afilm thickness, film thickness uniformity in an in-surface direction,and film thickness uniformity in an inter-surface direction of a siliconoxide film formed by using the method of the present embodiment (when aload temperature is 450° C. which is higher by about 50° C. than a filmformation temperature of 400° C.) were measured (an embodiment). In theembodiment, the silicon oxide films were measured at four positionshaving different distances (boat positions) from a top end of the waferboat 11. Also, for comparison, a film thickness, film thicknessuniformity in an in-surface direction, and film thickness uniformity inan inter-surface direction of a silicon oxide film formed by the samemethod when a load temperature is 400° C. which is the same as a filmformation temperature of 400° C. were measured (a comparative example).Results are shown in FIG. 4.

As shown in FIG. 4, in the embodiment, the silicon oxide films wereformed to have almost uniform film thicknesses at all of the boatpositions. In particular, even at the lower portion (the BTM portion) inthe reaction pipe 2 where a temperature is easily unstable, the siliconoxide films were formed to have almost the same film thicknesses asthose at other portions. Meanwhile, in the comparative example, whilethe silicon oxide films at an upper portion and a central portion in thereaction pipe 2 were formed to have almost the same film thicknesses asthose at other portions, the silicon oxide films at the BTM portion wereformed to have film thicknesses different from those at other portions,unlike in the embodiment. Accordingly, the embodiment has better filmthickness uniformity in an inter-surface direction than the comparativeexample. Also, when it comes to film thickness uniformity in anin-surface direction, the embodiment and the comparative example havelittle difference. As such, it is found that a silicon oxide film havingexcellent film thickness uniformity in an inter-surface direction isformed at a low temperature by performing the method of forming thesilicon oxide film according to the present embodiment.

Also, when the same measurement was performed when a load temperature ishigher by 20° C., 40° C., 60° C., or 80° C. than a film formationtemperature, silicon oxide films at almost all boat positions wereformed to have almost the same film thicknesses and thus film thicknessuniformity in an inter-surface direction is excellent.

As described above, according to the present embodiment, since a loadtemperature is set to a temperature higher than a film formationtemperature, a silicon oxide film having excellent film thicknessuniformity in an inter-surface direction may be formed at a lowtemperature.

Also, the present invention is not limited to the above embodiment, andvarious modifications and changes may be made. Another embodiment towhich the present invention may be applied will be explained.

Although a case where silicon oxide films are formed on thesemiconductor wafers W has been explained in the above embodiment, athin film is not limited to the silicon oxide film and any of variousthin films such as a silicon nitride film may be formed.

Although a case where DIPAS is used as a Si source gas (e.g., an organicSi source gas) and ozone is used as an oxidizing gas has been explainedin the above embodiment, the organic Si source gas is not limited toDIPAS and any of various gases which have a high adsorptive force at alow temperature may be used. When silicon oxide films are formed on thesemiconductor wafers W, a monovalent or divalent aminosilane gas may beused as the organic Si source gas.

The oxidizing gas is not limited to ozone, and oxygen or vapor may beused. In this case, since an ozone generating apparatus for generatingozone does not need to be used, a structure of the apparatus may besimplified. Meanwhile, when ozone is used as the oxidizing gas, a filmformation temperature may be set to be low.

Although a case where a film formation temperature is 400° C. has beenexplained in the above embodiment, the film formation temperature is notlimited to 400° C., and may range from a room temperature to 600° C.However, there is a preferable temperature range according to a type ofa used organic Si source gas. For example, when TDMAS is used as anorganic Si source gas, a film formation temperature may be set to rangefrom a room temperature to 550° C., and when BTBAS is used, the filmformation temperature may be set to range from a room temperature to600° C.

Although a case where both a film formation temperature of an adsorbingstep and a film formation temperature of an oxidizing step are 400° C.has been explained in the above embodiment, the film formationtemperature of the adsorbing step and the film formation temperature ofthe oxidizing step may be different from each other. In this case, bysetting a load temperature to a temperature higher, in particular, by20° C. to 80° C., than the film formation temperature of the adsorbingstep, silicon oxide films having excellent film thickness uniformity inan inter-surface direction may be formed at a low temperature.

Although a case where a batch type heat treatment apparatus having asingle pipe structure is used as a heat treatment apparatus has beenexplained in the above embodiment, the present invention may be appliedto a batch type vertical heat treatment apparatus having a double pipestructure in which the reaction pipe 2 includes an inner pipe and anouter pipe. Also, as shown in FIG. 5, a heat treatment apparatus 21 inwhich a plasma generator 22 is disposed may be used. In the heattreatment apparatus 21, oxygen or the like is supplied from the processgas introducing pipe 17 to pass through the plasma generator 22, andthus oxygen radicals having oxygen as radicals are generated and aresupplied into the reaction pipe 2.

The control unit 100 according to the embodiment of the presentinvention is not limited to a dedicated system, and may be realized byusing a general computer system. For example, the control unit 100 forperforming the aforesaid processes may be configured by installing aprogram in a general-purpose computer from a recording medium (e.g., aflexible disc or a compact disc (CD)-ROM) in which the program forexecuting the aforesaid processes is stored.

Any unit for supplying the program may be used. The program may besupplied through a predetermined recording medium as described above, orthrough a communication line, a communication network, a communicationsystem, or the like. In this case, the program may be posted on, forexample, a bulletin board system (BBS) of a communication network, maybe added to a carrier wave, and may be provided through the network. Theaforesaid processes may be performed by starting the provided programunder the control of an operating system (OS), like other applicationprograms.

The present invention may be used for forming thin films at a lowtemperature.

According to the present invention, thin films having excellent filmthickness uniformity in an inter-surface direction may be formed at alow temperature.

What is claimed is:
 1. A thin film forming apparatus comprising: areaction chamber in which an object is received; a heating unit whichheats the reaction chamber to a predetermined temperature; a filmforming gas supply unit which supplies a film forming gas into thereaction chamber; and a control unit which controls each portion of thefilm forming apparatus, wherein the control unit heats the reactionchamber to a load temperature by controlling the heating unit, and thenmakes the object received in the reaction chamber, heats the reactionchamber to a film formation temperature by controlling the heating unit,and then forms a thin film on the object by supplying a film forming gasinto the reaction chamber by controlling the film forming gas supplyunit, and sets the load temperature to a temperature higher than thefilm formation temperature.
 2. A non-transitory computer-readable mediumstoring a program for enabling a computer to serve as a heating unitwhich heats a reaction chamber, in which an object is received, to apredetermined temperature; a film forming gas supply unit which suppliesa film forming gas into the reaction chamber; and a film forming unitwhich heats the reaction chamber to a load temperature by controllingthe heating unit and then makes the object received in the reactionchamber, heats the reaction chamber to a film formation temperature bycontrolling the heating unit and then forms a thin film on the object bysupplying a film forming gas into the reaction chamber by controllingthe film forming gas supply unit, and sets the load temperature to atemperature higher than the film formation temperature.